Two novel filamentous bacterial isolates, strains WR-30T and WR-220, with an optimum growth temperature of approximately 55-60 degrees C were isolated from Wu-rai hot springs in the northern part of Taiwan. These isolates were aerobic, thermophilic, non-sporulating, red-pigmented and heterotrophic and formed extremely long, filamentous trichomes from cells of different lengths. Phylogenetic analysis of 16S rDNA, DNA-DNA hybridization, morphological and biochemical features and fatty acid composition revealed that the isolates represent a novel species of the genus Meiothermus. The name Meiothermus taiwanensis sp. nov. is proposed for this novel species. The type strain of M. taiwanensis is strain WR-30T (= ATCC BAA-399T = CCRC 17170T = DSM 14542T); strain WR-220 (= ATCC BAA400 = CCRC 17171 = DSM 14543) is a reference strain.